---
title: LookupExpression type | Wartiva GraphQL API
description: Lookup represents an nftables expression for looking up a value in a set or map. Wartiva GraphQL API reference with arguments, fields, and examples.
url: https://wartiva.com/api-docs/types/lookup-expression.html
updated: 2026-10-07
---

Endpoint configuration · GraphQL type

# `LookupExpression` type

Lookup represents an nftables expression for looking up a value in a set or map. This allows rules to efficiently check for membership or retrieve associated data.

## Fields

| Field Name | Description |
|---|---|
| `sourceRegister` - [`NftRegister!`](https://wartiva.com/api-docs/types/nft-register.html) | The register holding the key value to look up in the set. |
| `destRegister` - [`NftRegister!`](https://wartiva.com/api-docs/types/nft-register.html) | The register where the result of the lookup (e.g., associated data for maps) will be stored. |
| `isDestRegSet` - [`Boolean!`](https://wartiva.com/api-docs/types/boolean.html) | If true, the 'destRegister' field indicates that the lookup should populate this register with the result (e.g., the mapped value). If false, it's typically a membership check. |
| `setID` - [`Uint32!`](https://wartiva.com/api-docs/types/uint32.html) | The internal numeric ID of the target set or map. |
| `setName` - [`String!`](https://wartiva.com/api-docs/types/string.html) | The human-readable name of the target set or map. |
| `invert` - [`Boolean!`](https://wartiva.com/api-docs/types/boolean.html) | If true, the lookup result is inverted (e.g., matches if the key is *not* found). |

## Used by

- [`ChainExpression`](https://wartiva.com/api-docs/types/chain-expression.html) union: A union of all possible nftables chain expression types.

## Example

### Example

```json
{
  "sourceRegister": "VERDICT",
  "destRegister": "VERDICT",
  "isDestRegSet": false,
  "setID": "1073741824",
  "setName": "abc123",
  "invert": true
}

```

---

Wartiva is in early access. Request access: https://wartiva.com/early-access.html  
All pages: https://wartiva.com/llms.txt